1. Technical Field
The present invention relates to a semiconductor device and a method of fabricating the same.
2. Description of the Related Art
With the miniaturization of transistors, the speed and the integration of semiconductor devices constantly increase. In the meantime, however, metal lines become narrower, which increases a circuit delay, thereby prohibiting even higher speeds of the transistors.
To alleviate the problem of increased circuit delay due to miniaturization of metal lines, metal lines that use copper together with an aluminum alloy have been developed. Copper has a low resistance and a high electro-migration (EM) resistance, and the aluminum alloy can be used as a metal line material of large scale integration (LSI). However, copper is not easily etched and oxidized during processes. Thus, a damascene process is used for forming a copper metal line.
In the damascene process, a trench in which a top layer metal line is to be formed, and a via hole in which a contact plug connecting the top layer metal line to a bottom layer metal line or a substrate is to be formed, are formed in an insulation layer. Then, a metal such as copper is filled in the trench and the via hole, and planarized by a chemical mechanical polishing (CMP) process. The damascene process includes a single damascene process that separately forms a via plug and a trench, and a dual damascene process that simultaneously forms a via plug and a trench.
An electroplating method is proposed to fill the via hole and the trench with copper during the damascene process. The electroplating method forms a copper layer using an electrolyte containing a copper solute and an acid solvent.
However, when the trench or the via hole of a high aspect ratio is electro-deposited using the electroplating method, defects such as voids and seams can be formed. These defects can reduce life of the copper metal line, and thus need to be prevented. One solution is to add an additive to a plating solution, where the additive is adsorbed on each portion of a trench to control a copper electrodeposition speed. Therefore, the trench with a high aspect ratio can be formed without defects.